Bulletin of the American Physical Society
APS April Meeting 2020
Volume 65, Number 2
Saturday–Tuesday, April 18–21, 2020; Washington D.C.
Session Q14: Probing the Standard Model at CollidersLive
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Sponsoring Units: DPF Chair: Jinlong Zhang, Argonne National Laboratory Room: Virginia A |
Monday, April 20, 2020 10:45AM - 10:57AM Live |
Q14.00001: Performance of the ATLAS missing transverse momentum trigger during Run 2 pp collisions at sqrt(s) = 13 TeV Benjamin Carlson, Tae Min Hong The missing transverse momentum trigger (MET) is used for searches involving dark matter, supersymmetry, Standard Model processes, and many other measurements. The MET algorithms used to reduce the impact of pileup at level-1 (L1) and the high level trigger (HLT) will be discussed. Their limitations and improvements for L1 and the HLT developed during Run 2 will be shown. [Preview Abstract] |
Monday, April 20, 2020 10:57AM - 11:09AM Live |
Q14.00002: Complete measurement of the top-quark polarisation in \tch single top-quark production in $pp$ collisions at $\sqrt{s}=$ 13 TeV with the ATLAS detector Runyu Bi, Joseph Boudreau, Nello Bruscino, Susana Carbrera Urban, Maria Jose Costa, Marcus De Beurs, Carlos Escobar, Oscar Estrada Pastor, Jose Enrique Garcia Navarro, Galo Rafael Gonzalvo Rodriguez, Pablo Martinez Agullo, James Mueller, Chi Wing Ng, Marcel Vreeswijk At the LHC, electroweak production of single top quarks in the $t$-channel leads, in the standard model, to a high degree of top quark polarization. Two subprocesses, $u b \rightarrow d t$ and $\bar{d} b \rightarrow \bar{u} t$ contribute to $t$-channel production of single top, while the charge-conjugate processes contribute to production of antitop. The top (antitop) quark is expected to be polarized along the direction of the scattered light-quark (or "spectator" quark), and opposite to that direction for antitop production. This talk presents a measurement of the top quark polarization produced within a fiducial region of acceptance, using an integrated luminosity 139 fb$^{-1}$ of proton-proton collisions at 13 TeV, collected by the ATLAS detector. From the angular distribution of top quark decay products, we obtain all three components of the polarization of both top quarks and top antiquarks. In addition, differential angular distributions for angles $θ_{lx},θ_{ly},θ_{lz}$ unfolded at particle level, for events lying within the fiducial acceptance of the analysis are also provided. [Preview Abstract] |
Monday, April 20, 2020 11:09AM - 11:21AM Live |
Q14.00003: WWW triboson production using 139 fb$^{-1}$ of data taken by the ATLAS detector Wenhao Xu The joint production of three heavy vector bosons is a rare process in the Standard Model (SM) of particle physics and is one of the least studied SM process. Studies of triboson production can test the non-Abelian gauge structure of the SM theory and any deviations from the SM prediction would indicate hints of new physics at higher energy scales. I will present the full run2 study of $WWW$ triboson production using data collected in $pp$ collisions at $\sqrt{s}=13 $ TeV with the ATLAS detector between 2015 and 2018, corresponding to an integrated luminosity of 139 fb$^{-1}$. In the measurement, events containing two same-sign leptons and at least two jets are selected for the $WWW \rightarrow \ell \nu \ell \nu qq$ channel, while events with three leptons without any same-flavor opposite-sign leptons are used for the $WWW \rightarrow \ell \nu \ell \nu \ell \nu$ channel. Detailed results will be presented. [Preview Abstract] |
Monday, April 20, 2020 11:21AM - 11:33AM Live |
Q14.00004: Study of Longitudinal-Longitudinal WZ interactions using inclusive WZ$\to \ell \nu \ell \ell $ events Sydney Erickson, Prachi Atmasiddha, Junjie Zhu In the Standard Model of particle physics, the Higgs field spontaneously breaks the underlying electroweak symmetries resulting in a massive Higgs boson and three massless Goldstone bosons. These Goldstone bosons are absorbed into the W and Z bosons and become their longitudinal components and thus make them massive. It is critical to study longitudinal-longitudinal (LL) vector boson interactions. Normally people use vector boson scattering (VBS) events to study LL vector boson interactions. We propose to use the inclusive WZ$\to \ell \nu \ell \ell $ ($\ell =$e, $\mu )$ sample to study LL WZ interactions (W$_{\mathrm{L}}$Z$_{\mathrm{L}})$. We apply selection criteria on the Z boson transverse momentum and the angle of the W boson in the WZ rest frame with respect to the lab z-axis to improve the separation between the signal process (W$_{\mathrm{L}}$Z$_{\mathrm{L}})$ and background processes (W$_{\mathrm{L}}$Z$_{\mathrm{T}}$, W$_{\mathrm{T}}$Z$_{\mathrm{L}}$, W$_{\mathrm{T}}$Z$_{\mathrm{T}})$. Our truth-level study indicates that S:B can be increased from \textasciitilde 1:150 to \textasciitilde 1:1. We will also present sensitivity studies with detector effects included assuming 150 fb$^{\mathrm{-1}}$ of data at 13 TeV collected by the ATLAS or CMS detector. [Preview Abstract] |
Monday, April 20, 2020 11:33AM - 11:45AM Live |
Q14.00005: Precision Jet Substructure Measurements with ATLAS Run 2 Data Matt LeBlanc Theoretical calculations for jet substructure observables with accuracy beyond leading-logarithm have recently become available. Such well-understood observables provide novel probes of QCD in a new, collinear regime at the LHC. This talk presents new measurements of jet substructure observables by the ATLAS collaboration using Run 2 LHC data. These measurements are unfolded to particle-level to make comparisons with Monte Carlo simulations and state-of-the-art analytical calculations. [Preview Abstract] |
Monday, April 20, 2020 11:45AM - 11:57AM Live |
Q14.00006: Gap between jets at the LHC at next-to-leading order Christophe Royon We will present new calculations of gap between jets processes at the LHC. The gap is described using a BFKL pomeron exchange between two gluons. For the first time, the next-to-leading kernel and impact factor are used that allow to perform a full NLO calculation. The theoretical calculation is compared to recent measurement at the Tevatron and the :HC. [Preview Abstract] |
Monday, April 20, 2020 11:57AM - 12:09PM |
Q14.00007: A Search for Slow Massive Object Pairs (SMOPs) at the Large Hadron Collider Ethan Cannaert In the study of jets at the Large Hadron Collider, it is advantageous to make use of alternate event reference frames in order to elucidate the kinematics of highly complex events. Such techniques are a powerful tool for obtaining a coherent view of the underlying physics in these events, and can be used to look for new particles and new physics. In particular, boosting into certain reference frames is a useful tool for studying slow massive object pairs (SMOPs). Using data from the CMS experiment at the Large Hadron Collider and the technique described above, a search for such particles is conducted. [Preview Abstract] |
Monday, April 20, 2020 12:09PM - 12:21PM Not Participating |
Q14.00008: Present status of the K$_{\mathrm{L}}\to \quad \pi \iota ^{\mathrm{0}}\nu \nu $ search with the KOTO detector at J-PARC Brian Beckford The KOTO experiment at J-PARC continues its effort to observe and study the K$_{\mathrm{L}}\to \quad \pi \iota^{\mathrm{0}}\nu \nu $ decay. One of the best methods to search for new physics (NP) is to look for events that are theoretically clean and exceedingly rare. The Standard Model (SM) prediction for this (FCNC) process is 3.0 x 10$^{\mathrm{-11}}$ with minor uncertainties, making it an ideal process to investigate. From the experimental runs in 2015, KOTO set an experimental upper limit on the branching fraction to be \textless 3.0 x 10$^{\mathrm{-9}}$. The branching ratio is proportional to the height of the kaon unitary triangle and any observation above the SM prediction would be a clear signature of physics beyond the SM (BSM). The decay is identified by a pair of photons from the $\pi^{\mathrm{0}}$ decay and no other particles detected. KOTO used a Cesium Iodide (CSI) electromagnetic calorimeter to measure the energies and positions of the photons. The decay volume was surrounded by hermetic veto counters to ensure that there were no other particles. We analyzed data taken in 2016-2018 from 3.1 x 10$^{\mathrm{19\thinspace }}$protons on target (POT). This presentation will present the status of KOTO with data taken in 2016-2018 and the future outlook of the search for K$_{\mathrm{L}}\to $ $\pi \iota^{\mathrm{0}}\nu \nu $. [Preview Abstract] |
Monday, April 20, 2020 12:21PM - 12:33PM Not Participating |
Q14.00009: NNLO $t$-channel single-top-quark production revisited Zack Sullivan, John Campbell, Tobias Neumann Single-top-quark production is an important channel for measuring the top-quark mass, the Cabibbo-Kobayashi-Maskawa matrix element $V_{tb}$, and provides strong constraints on the parton distribution functions. Previous NNLO QCD calculations of $t$-channel production disagree by 100\% of the size of the NNLO correction, and are limited to using to top-quark mass as a fixed choice of scale. We present a new fully differential NNLO calculation that allows for a variety of scale choices and tracks $b$-flavored jets. [Preview Abstract] |
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